Fin heat exchanger comprising improved louvres

ABSTRACT

The invention relates to a heat exchanger comprising:
         at least one fin ( 4 );   at least one row of tubes ( 2 ), the tubes being connected to the fin ( 4 ) by clamping the tubes ( 2 ) in a collar ( 6 ) formed in the fin ( 4 ); and   at least one row ( 10 ) of louvers ( 12 ), said row ( 10 ) being formed in the fin ( 4 ) and interposed between two tubes ( 2 ) in the row of tubes, each louver ( 12 ) comprising a blade ( 14 ) provided with a free edge ( 16 ) and a connecting edge ( 18 ) connecting the louver ( 12 ) to the fin ( 4 ).       

     The connecting edge ( 18 ) of the blade ( 14 ) of at least the first louver ( 12 ) in the row ( 10 ) forms an upstream edge with respect to the air flow, the free edge ( 16 ) of the blade ( 14 ) forming the downstream edge.

The present invention relates to a heat exchanger, and more particularly to the tubes for a mechanical heat exchanger.

A heat exchanger generally comprises tubes, through which a heat transfer fluid is intended to flow, and heat exchange elements connected to these tubes.

A distinction is usually made between brazed heat exchangers and mechanical heat exchangers depending on the method for manufacturing them.

In a mechanical heat exchanger, the heat exchange elements, referred to as “fins” in this case, are connected to the tubes in the following way. First of all, through-holes for the tubes to pass through are made in the fins. These through-holes are generally each delimited by a raised edge forming a neck. Next, the fins are disposed substantially parallel to one another and each tube is inserted into a series of aligned holes in the fins. Finally, a radial expansion of the tubes is brought about by passing an expansion tool through the inside of these tubes so as to mechanically join the tubes and the fins by crimping, the necks delimiting the through-holes for the tubes then forming collars clamped around the tubes.

Such heat exchangers are passed through by an air flow, the fins extending across the flow.

In order to increase the heat exchange between the fins and the air flow, deflectors formed of rows of louvers are usually provided on the fins, the rows being interposed between the tubes in one and the same row of tubes. Generally, each louver comprises a blade provided with a free edge and a connecting edge that connects the louver to the fin.

In the prior art, the louvers are arranged in two successive groups of louvers in the row. For the louvers of the first group, to which the first louver of the row belongs, the free edge of the blades forms an upstream edge with respect to the air flow, the connecting edge forming the downstream edge. By contrast, for the louvers of the second group, to which the last louver of the row belongs, the connecting edge of the blades of the louvers forms an upstream edge with respect to the air flow, the free edge forming the downstream edge.

It has been found that this configuration has the effect of creating ineffective regions upon contact with louvers, in which the flow of air is braked, and so the heat exchange between the fin and the air flow is reduced.

The aim of the invention is to improve the performance of the heat exchanger by choosing a configuration of the louvers which makes it possible to limit the occurrence of these ineffective regions.

To this end, the subject of the invention is a heat exchanger comprising:

-   -   at least one row of tubes,     -   at least one fin disposed transversely to said row of tubes; the         tubes being connected to the fin by clamping the tubes in a         collar formed in the fin; and     -   at least one row of louvers, said row being formed in the fin         and interposed between two tubes in the row of tubes, each         louver comprising a blade provided with a free edge and a         connecting edge connecting the louver to the fin,

characterized in that the connecting edge of the blade of at least the first louver in the row forms an upstream edge with respect to the air flow, the free edge of the blade forming the downstream edge.

It has been found, surprisingly, that the configuration in which the connecting edge of the blade of at least the first louver forms an upstream edge with respect to the air flow passing through the fin and its free edge forms the downstream edge makes the air flow passing through the louvers less turbulent. This has the effect of limiting the occurrence of ineffective regions, and thus of increasing the heat exchange between the louvers and the air flow.

In this regard, tests have revealed an increase in the heat exchange of 3% for an equivalent pressure drop compared with the configurations of the prior art.

According to a first embodiment of the invention, the heat exchange has only one row of tubes, and the connecting edges of all the blades in the row form an upstream edge with respect to the air flow, the free edge of the blades forming the downstream edge.

According to a second embodiment of the invention, the free edge of at least the blade in the row forms an upstream edge with respect to the air flow, the connecting edge of this blade forming the downstream edge.

According to one particular embodiment of the invention, the row of louvers comprises two groups of louvers, the louvers of the second group following the louvers of the first group in the row of louvers, the connecting edge of the blades of the first group forming the upstream edge with respect to the air flow, the free edge of the blades of the first group forming the downstream edge, and the free edge of the blades of the second group forming the upstream edge with respect to the air flow, the connecting edge of the blades of the second group forming the downstream edge.

According to one particular embodiment of the invention, the two groups of louvers comprise equal numbers of louvers.

According to one particular embodiment of the invention, the free edge of the blade of the last louver of the first group is connected to the free edge of the blade of the first louver of the second group by a joining blade that forms a bridge substantially parallel to the surface of the fin.

According to one particular embodiment of the invention, the dimension of the joining blade between the free edge of the blade of the last louver of the first group and the free edge of the blade of the first louver of the second group is less than 3 mm.

The invention will be understood better from reading the following description, which is given solely by way of example and with reference to the drawings, in which:

FIG. 1 is a perspective view of a fin of a heat exchanger according to a first embodiment of the invention;

FIG. 2 is a perspective view of a fin of a heat exchanger according to a second embodiment of the invention;

FIG. 3 is a perspective view of a heat exchanger according to the invention.

FIG. 3 shows a mechanical heat exchanger 1 intended to equip a motor vehicle.

The heat exchanger comprises a row of tubes 2 (shown in a truncated manner for reasons of clarity in FIGS. 1 and 2), through which a conventional heat transfer fluid is intended to flow, and fins 4 (only one of which is shown for reasons of clarity) connected to these tubes 2.

The tubes 2 are connected to the fins 4 by clamping the tubes in collars 6 formed in the fins 4. To this end, the fins 4 are provided with through-holes 8 for the tubes to pass through. These through-holes 8 have an oblong overall shape.

In the example described, the tubes 2 each have an elongate overall shape and have a substantially oblong cross section. The tubes 2 are arranged substantially parallel to one another, so as to form a single row.

The fins 4 have a substantially flat rectangular overall shape and are arranged in the heat exchanger 1 in a manner substantially parallel to one another and perpendicular to the longitudinal directions of the tubes 2.

The fins 4 are intended to extend across an air flow from upstream to downstream, itself passing through the heat exchanger. Arrows F indicate the direction of travel of the flow.

In order to increase the heat exchange between the flow F and the fins 4, the heat exchanger 1 also comprises rows 10 of louvers 12, which are formed in each fin 4 and are each interposed between two tubes 2.

Each louver 12 comprises a blade 14 comprising a free edge 16 and a connecting edge 18 that connects the louver 12 to the fin 4.

In the two embodiments according to the invention, which are shown in FIGS. 1 and 2, the connecting edge 18 of the blade 14 of at least the first louver 12 in the row 10 forms an upstream edge with respect to the flow F, the free edge 16 of the blade 14 forming the downstream edge.

More particularly, in the first embodiment, shown in FIG. 1, the connecting edges 18 of all the blades 14 in the row 10 form an upstream edge with respect to the air flow F, the free edge 16 of the blades 14 forming the downstream edge.

In the second embodiment according to the invention, shown in FIG. 2, the free edge 16 of at least the last blade 14 in the row 10 forms an upstream edge with respect to the air flow F, the connecting edge 18 thereof forming the downstream edge.

More particularly, in this second embodiment, the row 10 comprises two groups of louvers 12, preferably comprising equal numbers of louvers 12, the louvers 12 of the second group following the louvers of the first group in the row 10 of louvers.

In the example shown in FIG. 2, the row 10 is formed of fourteen louvers 12 that are distributed in two groups of seven louvers 12, disposed on either side of a joining blade 20 that connects the free edge 16 of the last blade 14 of the first group to the free edge 16 of the first blade 14 of the second group.

For all the louvers 12 of the first group, the connecting edge 18 of each blade 14 forms an upstream edge with respect to the air flow F and the free edge 16 forms the downstream edge.

By contrast, for the louvers 12 of the second group, the free edge 16 of each blade 14 forms the upstream edge with respect to the air flow F, and the connecting edge 18 forms the downstream edge.

The joining blade 20 forms a bridge substantially parallel to the surface of the fin 4 between the two groups of the row 10. Substantially parallel is understood as meaning that the bridge is situated in a plane offset with respect to the surface of the fin. Preferably, the dimension of the joining blade 22 between the free edge 16 of the blade 14 of the last louver 12 of the first group and the free edge 16 of the blade 14 of the first louver 12 of the second group is less than 3 mm.

The invention is not limited to the embodiments presented, and further embodiments will be clearly apparent to a person skilled in the art.

In particular, a combination of the different embodiments can be envisioned in order to obtain the desired effects. 

1. A heat exchanger comprising: at least one row of tubes; at least one fin disposed transversely to said row of tubes, the tubes being connected to the fin by clamping the tubes in a collar formed in the fin; and at least one row of louvers, said row being formed in the fin and interposed between two tubes in the row of tubes, each louver comprising a blade provided with a free edge and a connecting edge connecting the louver to the fin, wherein the connecting edge of the blade of at least the first louver in the row forms an upstream edge with respect to the air flow, the free edge of the blade forming the downstream edge.
 2. The heat exchanger as claimed in claim 1, wherein the heat exchanger has only one row of tubes, and wherein the connecting edges of all the blades in the row form an upstream edge with respect to the air flow, the free edge of the blades forming the downstream edge.
 3. The heat exchanger as claimed in claim 1, wherein the free edge of at least the last blade in the row forms an upstream edge with respect to the air flow, the connecting edge of this last blade forming the downstream edge.
 4. The heat exchanger as claimed in claim 3, wherein the row of louvers comprises two groups of louvers, the louvers of the second group following the louvers of the first group in the row of louvers, the connecting edge of the blades of the first group forming the upstream edge with respect to the air flow, the free edge of the blades of the first group forming the downstream edge, and the free edge of the blades of the second group forming the upstream edge with respect to the air flow, the connecting edge of the blades of the second group forming the downstream edge.
 5. The heat exchanger as claimed in claim 4, wherein the two groups of louvers comprise equal numbers of louvers.
 6. The heat exchanger as claimed in claim 4, wherein the free edge of the blade of the last louver of the first group is connected to the free edge of the blade of the first louver of the second group by a joining blade that forms a bridge substantially parallel to the surface of the fin.
 7. The heat exchanger as claimed in claim 6, wherein the dimension of the joining blade between the free edge of the blade of the last louver of the first group and the free edge of the blade of the first louver of the second group is less than 3 mm. 